Marine pipeline installation system and method

ABSTRACT

A marine pipeline installation system for laying an offshore pipeline and/or installing a subsea riser includes a pipeline launch tower, a pipeline guide provided at an elevated position for guiding said pipeline to the pipeline launch trajectory along said tower, one or more tensioners, an abandonment and recovery (A&amp;R) system including at least one A&amp;R cable and associated A&amp;R winch and a sheave arrangement with one or more sheaves supported by the pipeline launch tower at an upper position thereof. An auxiliary trolley is provided which is adapted to support the weight of the launched pipeline and which is movable along a rail in the pipeline launch trajectory when the one or more tensioner frames are in the retracted non-operable position, from a position above the uppermost tensioner to a position below the lowermost tensioner, the rail being supported by the pipeline launch tower.

The present invention relates to a marine pipeline installation systemaccording to the preamble of claim 1.

Such a system is known e.g. from WO2012/091556 from the same applicant.WO2009/134116 and WO2007/108673 of the same applicant describealternative pipeline installation systems comprising some of thefeatures of the preamble of claim 1. In the known systems the supportassembly of one or more tensioner frames is adapted to allow fordisplacement of the tensioner frame with respect to the tower between anactive position, wherein the pipeline launch trajectory extends throughthe tensioner frame between the tracks, so that the tracks can engage ona pipeline, and a retracted non-operable position, so that an auxiliarytrolley is moveable up and down in the pipeline launch trajectory.

The aim of the present invention was to provide an improved marinepipelaying system, or at least an alternative system. The inventionfurther aims to provide improved pipeline installation methods andsystems therefor. The invention also aims to provide an improved riserinstallation system and method.

This aim is achieved in that auxiliary trolley according to theinvention comprises:

-   -   an A&R connector allowing the A&R cable to be connected to the        auxiliary trolley at the position above the uppermost tensioner        and thereby allowing the auxiliary trolley to lower with the        launched pipeline suspended therefrom;    -   an A&R cable guide allowing the A&R cable to be guided by the        auxiliary trolley and pass along the auxiliary trolley during        A&R of the launched pipeline connected to the A&R cable, at        least at the position below the lowermost tensioner.

The marine pipeline installation system according to the presentinvention is a system for laying an offshore pipeline and/or installinga subsea riser, said system at least being adapted to carry out the reellay method. The system is suitable for laying flexible pipelines, aswell as rigid pipelines. The present invention also relates to theinstallation of pipeline in the form of a subsea riser, e.g. between awellhead and a vessel, drilling/production facility, etc. As will beelucidated later, the system may also be suitable for laying pipesections in a J-lay mode. In addition, the system may also be suitablefor installing accessories in or onto a pipeline, and for handing over(transferring) a launched pipeline from a first marine pipelineinstallation system according to the invention to a second marine systemwhich comprises a winch and a cable.

Preferably, the system according to the invention comprises a vessel,but alternatively the system could also be provided on a platform. Thevessel is e.g. a monohull vessel, a twin-hull vessel, a semi-submersiblevessel.

The system comprises one or more storage reels for storage of thepipeline to be installed, which storage reels may be provided on avessel. These may be storage reels having a vertical axis, such ascarousels, or having a horizontal axis. It is conceivable that the reelsare stored on deck of the vessel, but it is also possible to store theone or more reels in the hull of the vessel. Reel supply vessels may beprovided near the vessel according to the invention, to supply reelsprovided with new pipelines to the vessel, to replace the empty reels ofwhich the pipeline has been launched.

The marine pipeline installation system according to the invention isalso provided with a pipeline launch tower, which is adapted forlaunching the pipeline in a pipeline launch trajectory into the sea, inthe direction of the seabed. The pipeline launch trajectory extendsparallel with the tower, preferably adjacent the tower. It is alsoconceivable, in particular when the tower is of a derrick-typeconstruction, that the pipeline launch trajectory extends in the tower.In an embodiment where the marine pipeline installation system comprisesa vessel having a moonpool, such a tower is often, but not necessarily,placed adjacent or over the moonpool of the vessel, and the marinepipelaying system is adapted to lay pipeline through said moonpool. Itis also possible to place the tower at another suitable location, e.g.at the stern of the vessel. In general the term tower here refers to araised structure on the vessel. In a possible embodiment, the pipelinelaunch tower is mounted pivotably on said vessel to adjust inclinationof the tower.

A pipeline guide is provided at an elevated position for guiding saidpipeline to the pipeline launch trajectory along said tower. Preferablythe pipeline guide is provided at an elevated position on the tower. Thepipeline guide provides a curved path for guiding the pipeline. Knownpipeline guides include a large diameter pipeline guide wheel or asemi-circular guide structure, e.g. provided with rollers or chains.Possibly, the pipeline guide is provided moveable, e.g. retractable asdescribed in WO2012/091556.

As common for reel lay pipelaying systems, one or more pipelinetensioners are provided at different heights below the pipeline guidefor launching the pipeline. Commonly two tensioners are provided, butversions with one or three tensioners are also known. In practice, asingle tensioner can be designed to support a pipeline weight of morethan 50 tons, and tensioner capacities of more than 100 tons are alsonot uncommon.

Each tensioner comprises a tensioner frame and multiple tracks, alsocalled caterpillars, supported by said tensioner frame. The tracks,often three or four tracks, are adapted for engaging the pipeline andsupporting at least part of the weight of the launched pipeline. As isknown in the art, the tensioner frame is preferably a frame which formsan ‘annular frame structure’ extending around the pipeline launchtrajectory in normal operation, within which frame structure the tracksare mounted. The tensioner frame is supported via an associated supportassembly, preferably by the pipeline launch tower. Alternatively, aseparate tensioner support structure may be provided. In an embodiment,the tensioner frame is supported by parallel bar linkage on the tower.

The tracks are mounted in said tensioner frame in a movable manner inorder to allow for adjustment of the gap between the tracks toaccommodate various pipe diameters.

It is also known from the prior art to design the tensioner frame‘oversized’ with respect to regular pipeline diameters, so that the gapbetween the tracks can be increased to a large size which allows for thepassage of an accessory fitted on (the end of) or in the pipeline, e.g.a connector on the end of or in a flexible pipeline. Such connectors arebulky and have a diameter greater than the pipeline diameter.

A preferred embodiment of the pipeline launch tower used for layingrigid pipes further carries a radius controller and/or one or morestraightener tracks for conditioning the rigid pipe at a positionupstream of the one or more tensioners.

It is preferred to have a crane, preferably an offshore mast crane,provided on deck of the vessel for performing various operations ondeck, as well as from and to the vessel. The capacity of such crane maybe several hundreds of tons. In preferred embodiments, the crane is usedto move large objects to the pipeline launch trajectory.

The marine pipeline system according to the invention is also providedwith an abandonment and recovery (A&R) system comprising at least oneA&R cable and associated A&R winch, and a sheave arrangement with one ormore sheaves supported by the pipeline launch tower at an upper positionthereof. With one or more sheaves of the A&R sheave arrangement providedat an upper position of the pipeline launch tower an accessory ispositionable below the sheave arrangement and the handling of largeobjects on deck is possible.

According to the invention, the support assembly of one or moretensioner frames is adapted to allow for displacement of the tensionerframe with respect to the tower between an active position, wherein thepipeline launch trajectory extends through the tensioner frame betweenthe tracks, so that the tracks can engage on a pipeline, and a retractednon-operable position, so that the auxiliary trolley is moveable up anddown in the pipeline launch trajectory.

From the same applicant auxiliary trolleys are known that are adapted tosupport the weight of the launched pipeline. In WO2012091556 of the sameapplicant, an auxiliary trolley is described, here a embodied as atravelling clamp, which is adapted to support the weight of the launchedpipeline and which is movable along a rail in the pipeline launchtrajectory when the one or more tensioner frames are in the retractednon-operable position, from a position above the uppermost tensioner toa position below the lowermost tensioner, the rail being supported bythe pipeline launch tower.

Retraction the entire assembly of a tensioner frame and tracks mountedtherein to a retracted position creates a large ‘clear envelope’ iscreated around the pipeline launch trajectory. This ‘clear envelope’ or‘zone’ allows for the passage of the auxiliary trolley in the pipelinelaunch trajectory. Possibly, in the retracted position of the tensionerframe a clear envelope is present around the pipeline launch trajectoryhaving a minimum distance to said tensioner of at least one meter,preferably at least 2 meters.

Possibly, one or more actuators, e.g. hydraulic cylinders, are providedfor displacing the tensioner frame between the active and retractedposition.

The displacement of the tensioner frame can for example be achieved bydisplacing the tensioner frame in its entirety, e.g. retracting it intothe direction of the pipeline launch tower. Hence, the tensioner in itsretracted position is held in a shape corresponding to the tension inthe active position. In the retracted position, the pipeline launchtrajectory then thus extends outside and spaced from said retractedtensioner frame. In a possible embodiment, the tower comprises twospaced apart main beams interconnected by a number of cross beams andwherein the one or more tensioners in their retracted position arelocated at least partly between said main beams, wherein preferably across beam is positioned below and above each tensioner.

On the other hand, it is also conceivable that the support assemblyallows for a relative displacement of portions of the tensioner frame,thus allowing the frame to ‘open’. For example, the support assembly mayallow for displacement of a part of the tensioner frame comprising oneor two tracks, away from another part of the tensioner frame comprisingthe remaining tracks. This may be seen as the ‘opening of two arms’. Ina possible embodiment the annular frame structure has at least onehinged frame part which can be moved between a ‘closed position’,wherein the annular frame structure forms a closed annulus, and an‘opened position’, wherein the one or more hinged parts create a lateralopening in the frame structure over the height thereof, creating a clearenvelope. According to the invention, the most important effect of thedisplacement of the tensioner frame is that the tensioner fame and thetracks should be retracted to such an extent that the auxiliary trolleyis able to move up and down in the pipeline launch trajectory.

It is also envisaged that with a tensioner having an openable framestructure to prove a lateral opening therein, that the ‘clear envelope’is created by the combination of retraction of the frame structure andthe ‘opening’ of the frame structure. This means that in the retractedposition the tensioner frame is held ‘open’ to create the ‘clearenvelope’.

Furthermore, in WO2009/134116 of the same applicant, an auxiliarytrolley is also described, which is here provided with other sheaves ofthe A&R sheave arrangement. However, the here described marine pipelineinstallation system is not provided with retractable tensioners.

The advantage of the present invention is that the auxiliary trolleyassists in A&R functionality, and allows restraining of the A&R wire ata lower position than at an upper position of the pipeline launch tower,increasing vessel stability significantly. In addition, interaction ofthe A&R cable with the hull of the vessel, which may result in damagingthe A&R cable, is prevented as much as possible.

According to the invention, the auxiliary trolley comprises an A&Rconnector allowing the A&R cable to be connected to the auxiliarytrolley at the position above the uppermost tensioner and therebyallowing the auxiliary trolley to lower with the launched pipelinesuspended therefrom; and an A&R cable guide allowing the A&R cable to beguided by the auxiliary trolley and pass along the auxiliary trolleyduring A&R of the launched pipeline connected to the A&R cable, at leastat the position below the lowermost tensioner.

The A&R cable guide e.g. comprises A&R sheaves, cable guidance holes, aso-called socket storage or the like, provided that the guide allows theA&R cable to be guided by and pass along the auxiliary trolley.Preferably, the A&R cable remains engaged with the auxiliary trolley. Itis conceivable that the A&R cable can be disconnected from the trolley.Configurations wherein the A&R cable guide comprises a combination of asheave and a hole are also conceivable.

The A&R system comprises at least one A&R cable and associated A&Rwinch. In a possible embodiment, the A&R system comprises multiple A&Rcables and associated A&R winches. Preferably, each one of the A&Rwinches is provided with heave compensation. Preferably, the number ofA&R cable guides on the trolley equals or exceeds the number of A&Rcables. In case of a single A&R cable, the A&R cable guide on theauxiliary trolley is provided centrally, in the pipeline launchtrajectory, while in case of two or more A&R cables, a correspondingnumber of A&R cable guide are preferably provided on the auxiliarytrolley at opposite sides of the pipeline launch trajectory. Theadvantage of A&R cable guides at opposite sides of the pipeline launchtrajectory is that wire twisting is prevented, and in addition that thepipeline launch trajectory remains clear. For example, two A&R cableguides are provided at either side of the pipeline launch trajectory.

Possibly, the auxiliary trolley further comprises a horizontal guidealong which at least two A&R cable guides are moveable, e.g. via shiftcylinders, allowing one A&R cable guide to be positioned in the pipelinelaunch trajectory when a single fall A&R is applied, and two A&R cableguides to be positioned at opposite sides of the pipeline launchtrajectory in case of a dual fall A&R.

In a possible embodiment, a plurality of A&R sheaves is provided at anupper position of the pipeline launch tower, which are provided atopposite sides of the pipeline launch trajectory. Preferably, thesesheaves are movable relative to each other.

It is conceivable that the marine pipeline installation system mayswitch between a configuration having two or more A&R cables (‘multiplefall’), and associated upper sheaves and A&R cable guides, and aconfiguration having a single A&R cable (‘single fall’), and only asingle upper A&R sheave and single A&R cable guide. It is then desiredto move the A&R cable guides from a position wherein the A&R cableguides are at an equal distance from the pipeline launch trajectory to aposition wherein one or some A&R cable guides have moved aside, and oneA&R cable guides has moved into the pipeline launch trajectory.

In a possible embodiment, the auxiliary trolley further comprises aclamp, which is adapted to engage a pipeline, pipe section or accessoryin the pipeline launch trajectory, preferably at the position above theuppermost tensioner, and the auxiliary trolley is adapted to allow forlowering of the pipeline or pipe section or accessory. The clamp can forexample comprise a pipe clamp, a collar clamp-type or a frictionclamp-type and/or a pin connection. In an embodiment, a fitting piecewill be provided at the pipeline, pipe section, accessory or the like,which fitting piece is clamped by the clamp on the auxiliary trolley.Optionally, the clamp is provided with changeable inserts, to be able toengage with different objects. Optionally, the clamping means arereleasable from the auxiliary trolley.

In an embodiment having multiple A&R guides provided on the auxiliarytrolley at opposite sides of the pipeline launch trajectory, it ispossible to provide the clamp in the pipeline launch trajectory, betweenthe A&R guides.

Possibly, an auxiliary trolley winch is provided for moving theauxiliary trolley in the pipeline launch trajectory, which auxiliarytrolley winch preferably operates independently of the A&R winch, butalternatively contributes to the A&R capacity. The auxiliary trolleywinch is possibly provided with a constant tension control.

The auxiliary trolley is suspended from the pipeline launch tower. Arail is provided, preferably at the pipeline launch tower, along whichthe auxiliary trolley is moveable. An auxiliary trolley rail mayalternatively be provided on a separate structure. It is preferred to beable to lock the auxiliary trolley in its lowest position, for examplewith pins, to take the full A&R off lead and side lead forces.

In an embodiment, the auxiliary trolley allows for man-riding on thetrolley, in order to move personnel in the pipeline launch trajectory.

Preferably, the marine pipeline installation system further comprising aworking platform supported by a support frame in the upper part of thetower, whereby the support frame is adapted to allow for displacement ofthe working platform with respect to the tower, such that the workingplatform is movable into and out of the tower pipeline launchtrajectory. This is advantageous in operations where the pipeline isbeing cut at such an upper location, preferably above the one or moretensioners. As such, operations can be performed while the launchedpipeline is being held by the one or more tensioners. Skidding theworking platform out of the pipeline launch trajectory allows theauxiliary trolley to move up and down in the pipeline launch trajectory,past the working platform.

It is also conceivable that such a working platform is supported at alower part of the tower, as is known e.g. from our application WO2009/134116.

The marine pipeline installation system according to the presentinvention possibly further comprising a J-lay installation, which J-layinstallation includes at least: a pipe loader for sequentially supplyingpipe sections to an elevated position aligned with the pipeline launchtrajectory, a pipe section alignment device for aligning a pipe sectionwith the upper end of the previously launched pipeline and a pipesection work station, e.g. adapted for connecting the pipe section tothe launched pipeline. As such, a multifunctional pipeline installationsystem is provided.

Preferably, in such a system the auxiliary trolley is additionallyprovided with a pipe clamp which is adapted to engage a pipe section inthe pipeline launch trajectory above the uppermost tensioner, andwherein the auxiliary trolley is adapted to lower the pipe section, andpreferably also of the launched pipeline connected thereto. As a result,the auxiliary trolley can be used for performing J-lay operations.

Possibly, a pipeline is installed containing a pipeline part realized bypipeline coming from a reel using the reel lay method, and a furtherpart is realized by the J-lay method wherein sections of pipeline areadded sequentially to the launched pipeline, said one or more tensionersbeing employed during reel laying in their active position, and thetensioners being removed to allow for performing J-lay.

In a possible embodiment, the system further comprises a hang off modulearranged below said one or more tensioners, and preferably also belowthe lowermost position of the auxiliary trolley, which hang off moduleis adapted for clamping and supporting the weight of previously launchedpipeline.

The invention also relates to a method for installing an accessory ontoa pipeline to be laid on the seabed, wherein use is made of a marinepipeline installation system according to any of the preceding claims,further comprising a hang off clamp arranged below said one or moretensioners, comprising the following steps:

-   -   positioning the auxiliary trolley above the uppermost tensioner;    -   launching the pipeline from the one or more storage reels, via        the pipeline guide and via the one or more tensioners in their        active position, in the pipeline launch trajectory into the sea,    -   interrupting the launch of pipeline, cutting the pipeline and        hanging off the launched pipeline in the hang off module,    -   displacing the one or more tensioner frames from the active        position to the retracted position,    -   positioning the accessory in the pipeline launch trajectory,    -   attaching the accessory to the launched pipeline and to the        auxiliary trolley,    -   suspending the accessory and the launched pipeline from the A&R        system,    -   disengaging the hang off module from the launched pipeline,    -   lowering the accessory with the launched pipeline by the A&R        system.

Possibly, the accessory is a second end connector, provided at the endof a pipeline. The marine pipeline installation system of the inventionis advantageously adapted to handle such a second end connector. To thisend, a method of lowering a pipeline provided with a second endconnector, wherein use is made of a marine pipeline installation systemaccording to any of the preceding claims, further comprising a hang offclamp arranged below said one or more tensioners, comprising thefollowing steps:

-   -   positioning the auxiliary trolley above the uppermost tensioner        and connecting the A&R cable to the auxiliary trolley;    -   launching the pipeline from the one or more storage reels, via        the pipeline guide and via the one or more tensioners in their        active position, in the pipeline launch trajectory into the sea,    -   positioning the second end connector in the pipeline launch        trajectory,    -   interrupting the launch of pipeline,    -   attaching the second end connector to the auxiliary trolley,    -   suspending the second end connector and the launched pipeline        from the A&R system,    -   displacing the one or more tensioner frames from the active        position to the retracted position,    -   lowering the second end connector with the launched pipeline by        the auxiliary trolley,    -   interrupting the launch of second end connector with launched        pipeline and hanging off the second end connector in the hang        off module,    -   disconnecting the second end connector from the auxiliary        trolley,    -   disconnecting the A&R cable from the auxiliary trolley,        providing the A&R cable in the A&R cable guide,    -   connecting the A&R cable to the second end connector,    -   lowering the second end connector with the launched pipeline by        the A&R cable.

Possibly, the auxiliary trolley comprises pipe engagement means forengaging a pipe, and wherein the auxiliary trolley is used for carryingout the J-lay method, in particular for lowering of the pipe section.

The invention further relates to a method for transferring a launchedpipeline from a first marine pipeline installation system according toany of the claims 1-7 to a second marine system which comprises a winchand a cable, the method comprising the following steps:

-   -   positioning the auxiliary trolley above the uppermost tensioner;    -   launching the pipeline from the one or more storage reels, via        the pipeline guide and via the one or more tensioners in their        active position, in the pipeline launch trajectory into the sea,    -   interrupting the launch of pipeline and cutting the pipeline        above the one or more tensioners, the launched pipeline being        supported by the one or more tensioners,    -   attaching the launched pipeline to the auxiliary trolley and        connecting the A&R cable to the auxiliary trolley,    -   suspending the launched pipeline from the A&R system,    -   disengaging the one or more tensioners from launched pipeline        and displacing the one or more tensioner frames from the active        position to the retracted position,    -   attaching the cable of the second marine system to the launched        pipeline,    -   launching the launched pipeline by the at least one A&R cable        until the cable of the second marine system is taut,    -   detaching the launched pipeline from the auxiliary trolley and        support the launched pipeline from the winch of the second        marine system.

Another aspect of the invention relates to a marine pipelineinstallation system for laying an offshore pipeline and/or installing asubsea riser, wherein the system comprises:

-   -   a vessel comprising a hull and a deck,    -   a moonpool, extending through the hull of the vessel, wherein        the moonpool can be covered by a hatch assembly with one or more        movable hatch panels adapted to cover said moonpool at the level        of the deck,    -   a pipeline launch tower provided above or adjacent the moonpool,        which pipeline launch tower is adapted for launching the        pipeline in a pipeline launch trajectory through the moonpool        into the sea,    -   an abandonment and recovery (A&R) system comprising at least one        A&R cable and associated A&R winch, and an A&R sheave        arrangement with one or more sheaves supported by the pipeline        launch tower at an upper position thereof,        wherein one or more other sheaves of the A&R sheave arrangement        are provided on one or more of the moonpool hatches. This is        advantageous to prevent wire twisting, and has the advantage        that the pipeline launch trajectory remains clear.

This aspect may be used in combination with the first aspect of theinvention: an embodiment is conceivable wherein the A&R system comprisesa a sheave arrangement with one or more sheaves supported by thepipeline launch tower at an upper position thereof, and with one or moreother A&R cable guides are provided on an auxiliary trolley, which issuspended from the pipeline launch tower, and with one or more othersheaves of the A&R sheave arrangement are provided on one or more of themoonpool hatches.

The invention will be further elucidated in the drawings, in which:

FIG. 1 schematically shows a perspective view of a marine pipelineinstallation system according to the present invention;

FIG. 2 shows a portion of the pipeline launch tower of the system ofFIG. 1 in more detail in a perspective view;

FIG. 3a shows in detail an upper portion of the pipeline launch tower ofFIG. 1 in a perspective view, with a workstation in a retractedposition;

FIG. 3b shows the upper portion of FIG. 3a , with the workstation in thepipeline launch trajectory;

FIG. 4 shows in detail an upper portion of the pipeline launch tower ofFIG. 1 in a perspective view, with the tensioners and the upperworkstation in the retracted non-operable position;

FIG. 5 shows in detail an alternative embodiment of an upper portion ofa pipeline launch tower of a marine pipeline installation systemaccording to the present invention;

FIG. 6 shows in a perspective view an embodiment of a second aspect ofthe present invention;

FIGS. 7A-7B show side views of a part of an embodiment of an auxiliarytrolley to which an A&R cable is connected and a launched pipeline;

FIG. 7C shows a top view of the auxiliary trolley of FIGS. 7A and 7Bwithout the A&R cable and launched pipeline connected thereto;

FIG. 7D shows a perspective view of an exemplary A&R connector accordingto the invention;

FIG. 8A shows a side view of the auxiliary trolley of FIG. 7, withoutthe A&R cable and launched pipeline connected thereto;

FIG. 8B shows a front view of the auxiliary trolley of FIG. 7, with theA&R cable and launched pipeline connected thereto;

FIG. 8C shows a side view of part of the auxiliary trolley of FIG. 7,with the A&R cable connected thereto;

FIGS. 9 and 10 show alternative side views of a marine pipelineinstallation system according to the invention, with the auxiliarytrolley indicated in multiple alternative positions;

FIG. 11A shows the auxiliary trolley of FIG. 7 in a top view, positionA-A as indicated in FIG. 9;

FIG. 11B shows the auxiliary trolley of FIG. 7 in a top view, positionB-B as indicated in FIG. 9;

FIG. 11C shows the auxiliary trolley of FIG. 7 in a top view, positionC-C as indicated in FIG. 9;

FIG. 11D shows the auxiliary trolley of FIG. 7 in a top view, positionD-D as indicated in FIG. 9, in a single fall A&R position;

FIG. 11E shows the auxiliary trolley of FIG. 7 in a top view, positionD-D as indicated in FIG. 9, in a dual fall A&R position.

In FIG. 1 a marine pipeline installation system 1 for laying an offshorepipeline 5 and/or installing a subsea riser according to the inventionis shown in a perspective view. On the vessel 2, a storage reel 3 isprovided for storage of the pipeline 5 to be installed. Here a reel witha horizontal axis is provided, which horizontal axis is substantially atdeck level 2 b of the hull of the vessel. Alternatively, the reel may bemounted on a frame, provided on deck. Optionally, the frame is movablewith respect to the deck. Yet alternatively, a storage reel with avertical axis may be provided, which can be installed in the hull of thevessel or on top. Yet alternatively, it is also conceivable that aseparate vessel or platform or the like is provide comprising the one ormore storage reels.

On the deck 2 b of the vessel also a crane 4 is provided for assistingin various operations.

The marine pipeline installation system 1 comprises a pipeline launchtower 10 which is adapted for launching the pipeline 5 in a reel laymethod in a pipeline launch trajectory 11 into the sea. The pipelinelaunch trajectory 11 extends parallel and adjacent to the tower 10, intothe sea 20. The tower 10 is mounted pivotably about pivot axis 10 b onsaid vessel 2 to adjust inclination of the tower. To this end, so-calledadjusters 15 are provided supporting the tower in various angledpositions. In the shown embodiment, the tower 10 comprises two parallelcolumns 10 a, defining a H-shaped tower.

The pipeline launch tower 10 is mounted on the stern 2 a of a vessel 2.In an alternative, not shown embodiment, it is also conceivable to mountthe pipeline launch tower at a side of the vessel. Yet alternatively,the vessel may be provided with a moonpool in the hull of the vessel,adjacent or above which the pipeline launch tower 10 can also beprovided, allowing the pipeline launch trajectory to extend through themoonpool.

At an elevated position of the pipeline launch tower 10 a pipeline guide16 is provided for guiding said pipeline 5 to the pipeline launchtrajectory 11 along said tower 10. In this embodiment, the pipelineguide 16 is embodied as a round wheel, but it is also possible toprovide a semi-arcuate pipeline guide. This pipeline guide is alsoreferred to as the aligner, or the aligner wheel.

Upon laying rigid pipelines, a straightening assembly is required tostraighten the pipeline to be laid. In this embodiment, a straighteningassembly 17 is provided, of which two straightening tracks are visible.Commonly, straightening assemblies comprising 2 or 3 straighteningtracks are applied. When a flexible pipeline is being installed, nostraightening assembly is required. In the shown embodiment, a pipeclamp 19 is provided below the straightening assembly 17. Optionally,the straightening tracks, and possibly also the pipe clamp, areremovable from the pipeline launch trajectory. This is advantageous whenflexible pipelines are being installed, or when the pipeline launchtrajectory is made clear for other purposes such as accessoryinstallation, or A&R operations.

The reel lay method requires one or more tensioners 18 to install thepipeline: in the shown embodiment two tensioners 18 are provided. Eachtensioner 18 comprising a tensioner frame and multiple tracks (notvisible in detail in FIG. 1) supported by said tensioner frame, saidtracks being adapted for engaging the pipeline and supporting at leastpart of the weight of the launched pipeline.

The tensioner frame is supported via an associated support assembly,which, according to the invention, is adapted to allow for displacementof the tensioner frame with respect to the tower 10 between an activeposition, as visible in FIG. 1, wherein the pipeline launch trajectory11 extends through the tensioner frame and between the tracks, so thatthe tracks can engage on a pipeline, and a retracted non-operableposition, so that an auxiliary trolley is moveable up and down in thepipeline launch trajectory. More details of the tensioner and theauxiliary trolley will be described later.

The marine pipeline installation system further comprises an abandonmentand recovery (A&R) system 30, comprising at least one A&R cable 31 andassociated A&R winch 32, and a sheave arrangement with two sheaves 33supported at the stern side by the pipeline launch tower 10 at an upperposition thereof. In the shown embodiment, at the bow-side of the tower,a load equalizer 34 of the A&R system is visible.

According to the present invention, an auxiliary trolley 38 is providedcomprising two A&R cable guides, here two other sheaves of the A&Rsheave arrangement. The auxiliary trolley 38 is also suspended from thepipeline launch tower. More details of the auxiliary trolley will bedescribed later.

On the vessel 2 also a pipe loader 40 is provided, for sequentiallysupplying pipe sections to an elevated position of the pipeline launchtower 10 aligned with the pipeline launch trajectory 11. The systemfurther comprises a pipe section alignment device for aligning a pipesection with the upper end of the previously launched pipeline.Preferably, this pipe section alignment device is provided in thepipeline launch tower 10. Furthermore, a pipe section work station 45 isprovided, adapted for connecting the pipe section to the launchedpipeline. As such, the marine pipeline installation system according tothe invention can also be used for laying a pipeline in a J-lay modus.In the shown embodiment, the pipe loader 40 is also suitable for loadingaccessories 41 such as PLET's, as visible in FIG. 1.

FIG. 2 shows a portion of the pipeline launch tower 10 of FIG. 1 in moredetail. the FIGS. 3a and 3b show an upper portion of the pipeline launchtower 10 of FIG. 1 in detail. Same parts as visible in FIG. 1 are givensame numbers.

Here, the upper tensioner 18 is visible, comprising a tensioner frame 18a in which four tensioning tracks 18 b are supported. The tensioningtracks are adapted for engaging the pipeline 5 and supporting at leastpart of the pipeline weight, preferably the weight of the previouslylaunched pipeline. The tensioner frame 18 a is supported by anassociated support assembly 25, here comprising two sets of beamsconnecting the tensioner frame 18 a to the pipeline launch tower 10.According to the present invention, the support assembly 25 is adaptedto allow for displacement of the tensioner frame 18 a with respect tothe tower 10. To this end, the support assembly 25 as shown comprisesmultiple beams which are pivotably interconnected, such that, uponactuation, the tensioners are retracted between the columns 10 a of thetower 10.

Also visible in FIGS. 2a and 2b is an upper working platform 35, whichis supported by a support frame 35 a in the upper part of the tower. Thesupport frame 35 a is skiddable along a support frame guide 35 bprovided in the upper part of the tower 10. Preferably, the supportframe guide 35 b is substantially perpendicular to the tower pipelinelaunch trajectory. As such, the working platform 35 is movable into andout of the pipeline launch trajectory 11. In FIG. 2a , the workingplatform 35 is skidded out of the pipeline launch trajectory.Alternative embodiments without a support frame guide are alsoconceivable, e.g. comprising pivotably connected beams.

Above the upper working platform 35, the auxiliary trolley 38 and upperA&R sheaves 33 are visible in detail. On the auxiliary trolley two A&Rsheaves 26 are provided, over which two A&R cables 31 a and 31 b areguided. Both the upper A&R sheaves 33 and the auxiliary trolley sheaves26 are provided at opposite sides of the pipeline launch trajectory 11.

Also provided on the auxiliary trolley 38, below the A&R sheaves 26, aretwo A&R end connector catchers 27. The end connectors 28 are visible inFIGS. 2a and 2b . In the shown embodiment, the combination of an A&Rsheave 26 with an A&R end connector catcher 27 is provided on a carriage29 on the auxiliary trolley 38, as a result of which the sheaves andcatchers are movable in a horizontal direction towards and away from thepipeline launch trajectory 11. This may be advantageous to prevent wiretwisting, or alternatively when additional clamping means are providedon the auxiliary trolley 38, or for example when only a single A&R cableis required, which is to extend in the pipeline launch trajectory.

The above advantages may also require the upper A&R sheaves 33 to bemovable in a horizontal direction. In the shown embodiment this ispossible by actuators 33 a.

According to the present invention, the auxiliary trolley 38 is moveableup and down in the pipeline launch trajectory 11. In the shownembodiment, a pair of rails 39 is provided on the pipeline launch tower10. In particular, each column 10 a of the tower is provided with a rail39, across which the auxiliary trolley 38 is movable. The auxiliarytrolley is provided with an A&R connector, here the end connectorcatchers 27, allowing the A&R cable to be connected to the auxiliarytrolley at the position above the uppermost tensioner and therebyallowing the auxiliary trolley to lower with the launched pipelinesuspended therefrom.

In FIG. 4 the upper portion of the pipeline launch tower 10 is shown ina perspective view from above. Same parts as visible in FIG. 1 are givensame numbers. A pipeline is present in the pipeline launch trajectory11, which is held by the pipe clamp 19 provided below the straighteningassembly (not visible). Two A&R cables 31 a, 31 b are visible, eachadjacent, parallel and at opposite sides of the pipeline launchtrajectory 11. The upper A&R sheaves 33 are also visible, as well as theequalizing sheaves 34. At the bow side of the pipeline launch tower 10,the adjusters 15 and the crane 4 are visible. At the stern side of thepipeline launch tower 10, the tensioners 18 are no longer provided asthey are retracted to the non-operable position. On the other hand, itnow is visible that the auxiliary trolley is allowed to move to a lowerposition in the pipeline launch trajectory 11, along rails 39.

In FIG. 5 an alternative embodiment of an upper portion of a pipelinelaunch tower of a marine pipeline installation system according to thepresent invention is shown. Same parts as visible in FIG. 1 are givensame numbers. The pipeline launch tower of FIG. 5 differs from thepipeline launch tower of FIG. 1 in that here a semi-arcuate pipelineguide 116 is applied, which in the embodiment of FIG. 5 is providedbelow the upper A&R sheaves 33.

In the shown embodiment, the A&R sheaves have been removed from theauxiliary trolley 38. Instead, the auxiliary trolley 38 comprises aclamp 100, here a clamp that is releasable from the auxiliary trolley.The clamp 100 is provided in the pipeline launch trajectory 11 forengaging on a pipe section 110, here in an elevated position thereof. Assuch, the auxiliary trolley 38 can be used to allow for lowering of thepipe section 110.

Here, the clamp is embodied as a collar clamp. It is noted that ingeneral the clamp can be provided with different inserts, to adapt theclamp to different pipe diameters and/or collar types.

FIG. 6 shows in a perspective view an embodiment of a second aspect ofthe present invention. This aspect of the invention relates to a marinepipeline installation system 201 for laying an offshore pipeline and/orinstalling a subsea riser, wherein the system shown in this embodimentcomprises:

-   -   a vessel (not visible) comprising a hull (not visible) and a        deck 200,    -   a moonpool 220, extending through the hull of the vessel,        wherein the moonpool can be covered by a hatch assembly with one        or more movable hatch panels 210 adapted to cover said moonpool        220 at the level of the deck 200, which hatch panels are        preferably movable across rails 211 provided on deck 200,    -   a pipeline launch tower (not visible) provided above or adjacent        the moonpool, which pipeline launch tower is adapted for        launching the pipeline in a pipeline launch trajectory 213        through the moonpool 220 into the sea,    -   an abandonment and recovery (A&R) system comprising two A&R        cables 205, 206 and associated A&R winch (not visible), and a        sheave arrangement with two sheaves 233 supported by the        pipeline launch tower at an upper position thereof, and two        other sheaves 215 of the A&R sheave arrangement are provided on        the two moonpool hatches 210.

In FIGS. 7A-7B a side view of a part of an embodiment of an auxiliarytrolley 50 is shown, in alternative positions. The auxiliary trolley 50comprises an A&R connector 51, here embodied as a plate protrusion 51comprising a hole, to which a dedicated A&R connector part 52, shown indetail in perspective in FIG. 7D, is connectable. The dedicated A&Rconnector part 52 comprises an opening 52 c in the upper surfacethereof, through which the A&R cable is allowed to extend. In the shownembodiment, the A&R connector part furthermore comprises an opening 52 bat the side, allowing the A&R cable to be removed from the A&R connectorpart 52, or the A&R connector part 52 to be pivoted away from the A&Rcable. The A&R cable 53 comprises a cable part 53 a, only part of whichis shown, and a tapering end portion 53 b. The opening 52 c of the A&Rconnector part matches the diameter of the A&R cable, but is smallerthan the end portion 53 b, and thus prevents the A&R end portion 53 b topass through the opening 52 c. Thereby, a connection between the A&Rcable 53 and the auxiliary trolley 50 is established. It is noted thatpivoting the A&R connector part 52 away from the A&R cable is onlypossible when there is no load exerted to the A&R cable connected to theauxiliary trolley 50. Only in this situation, the end portion 53 b isallowed to be lowered with respect to the A&R connector part 52 and theA&R cable part 53 a to pass through the opening 52 b or vice versa.

In FIG. 7A a pipe 54 comprising a pipe end portion 54 a is shown, whichis connected via a bolt 55 a to a pipe fitting piece 55 to the auxiliarytrolley 50. In the configuration of FIG. 7A, the auxiliary trolley 50 isable to lower the launched pipeline with the A&R cable 53. The pipefitting piece 55 comprises a tapering end portion 55 b, which is adaptedto be clamped by a collar clamp 50 a on the auxiliary trolley 50. Inparticular, in the shown embodiment, the end portion 55 b is rounded,while the collar clamp is shaped cup-like, resulting in an articulatedjoint allowing rotation about rotation point 55R. This rotation of pipefitting piece 55 about point 55R in the collar clamp 50 allows for acompensation of length difference of the A&R cables. In FIG. 7B, arotation of the auxiliary trolley 50 is shown, compensating for a lengthdifference.

The collar clamp 50 a comprises two parts 50 a′ and 50 a″, visible inparticular in the top view of FIG. 7C, wherein collar clamp part 50 a′is essentially C-shaped, and the collar clamp part 50 a″ is formed by avery small remaining circle-segment. For clarity reasons, the A&Rconnector part 52 is not shown in FIG. 7C. The collar clamp 50 asurrounds the tapering end portion 55 b of the pipe fitting piece 55,and thereby supports the launched pipeline. The collar clamp 50 a isclosed in the embodiments shown in FIGS. 7A-7C, and is shown in openconfiguration in FIG. 8A.

Furthermore, in FIG. 7A it is visible that the auxiliary trolley 50comprises two A&R cable guides 50 b′ and 50 b″, here in line with theA&R connector 51, 52. The A&R cable guides 50 b′ and 50 b″ allow the A&Rcable 53 to be guided by the auxiliary trolley 50 and pass along theauxiliary trolley 50 during A&R of the launched pipeline connected tothe A&R cable. In the shown embodiment, the A&R cable guides areembodied as removable hardened valves for rope guidance. In the top viewof FIG. 7C, pad eyes 50 d are visible, which may be used for maintenancepurposes. The A&R cable guides 50 b′ and 50 b″ are possibly removablymounted in the auxiliary trolley 50, allowing replacement e.g. in caseof damage or other cable types.

In the configuration of FIG. 7B, the pipe 54 is clamped by a hang offclamp 56 a, 56 b, provided below the auxiliary trolley 50. Thissituation is envisaged when the auxiliary trolley 50 is at its lowermostposition, below the lowermost tensioner (not shown). By clamping thepipe, the load of the pipe 54 and possibly the launched pipelineconnected thereto is transferred from the auxiliary trolley 50 to thehang off clamp 56 a, 56 b. This allows the A&R cables, in particular theA&R cable end portions 53 b, to pass through the A&R cable guides 50 b′and 50 b″, and connect them directly or via a yoke or cross beam to apipeline, pipe portion or accessory. The A&R connector part 52 isallowed to pivot away from the A&R cable 53, and may optionally bedisconnected. This way, the A&R cable 53 is disconnected from theauxiliary trolley 50, but remains guided by the auxiliary trolley.

The removal of the load from the auxiliary trolley 50 additionallyallows the pipe fitting piece 55 to rotate about point 55R in the collarclamp 50. In this situation, the collar clamp 50 may be opened byallowing opposed sideways movements of the collar clamp parts 50 a′ and50 a″. As such, the pipe fitting piece 55 can be removed from theauxiliary trolley 50, thus disconnecting the pipe 54 from the auxiliarytrolley 50.

In particular, the shown embodiment of auxiliary trolley 50 comprisestwo trolley parts 50′ and 50″, each part comprising an A&R cable guide50 b′ and 50 b″ and a collar clamp part 50 a′, 50 a″.

The sideways movements of the collar clamp parts 50 a′ and 50 a″ isvisible in FIG. 8A, in which trolley part 50′ comprises collar clamppart 50 a′ and A&R cable guide 50 b′, and auxiliary part 50″ comprisescollar clamp part 50 a″ and A&R cable guide 50 b″. In FIG. 8A theauxiliary trolley 50 is shown in its entirety, including bogies 57 withwhich the auxiliary trolley 50 is movable along a rail 58 supported bythe pipeline launch tower (not shown). Furthermore, it is visible thatthe auxiliary trolley 50 comprises a horizontal guide 60, along whichthe two trolley parts 50′ and 50″ are movable via shift cylinders 60 a.The shift cylinders may have their own power pack, or alternatively befed by a drag chain, which will be explained later. The trolley partsare provided with frame parts 50 c′ and 50 c″, slidably engaging withthe horizontal guide 60. In relation to FIG. 7b , the advantageousrotation of pipe fitting piece 55 about point 55R in the collar clamp 50was described, allowing for a compensation of length difference of theA&R cables. This is only effective when the trolley is allowed torotate, as visible in FIG. 7B, which in the shown embodiment is possibleas the guide 60 comprises two parts, allowing a rotation about point60R, which is made possible by mutual flexibility of the bogies 57. Alength difference of up to 100 mm may preferably be compensated for.Hence, the auxiliary trolley acts as an equalizer.

In FIG. 8A, cooperating connector parts 50 e′ and 50 e″ of the twotrolley parts 50′ and 50″ are visible, which are shown interconnectedvia a pin locking cylinder 50 e as shown in FIGS. 7A, 7B and 8B. Thehydraulics for the locking pin are provided by drag chains 60 b, visiblein FIG. 8B.

FIGS. 9 and 10 show alternative side views of a marine pipelineinstallation system according to the invention, with the auxiliarytrolley indicated in multiple alternative positions. In particular, thesecond end handling process is elucidated in relation to FIGS. 9, 10 and11. This process of second end handling preferably takes place with thepipeline launch tower at an angle of 90° with respect to the vessel ontowhich it is mounted.

In FIGS. 9 and 20, a pipeline launch tower 70 is visible, which isadapted for launching the pipeline in a pipeline launch trajectory 71into the sea. The pipeline launch tower 70 is mounted pivotable abouthorizontal pivot axis 70 a onto the deck of a vessel 75, via one or moreadjusters 79 (only part of which is shown). In the vessel, a moonpool 75a is provided, through which the pipeline launch trajectory 71 extends.A pipeline guide 72 is provided at an elevated position of the tower 70,for guiding a pipeline to the pipeline launch trajectory 71.Furthermore, two tensioners 73 a, 73 b are visible, comprising atensioner frame and multiple tracks supported by the tensioner frame,which are not shown in detail. The tensioner tracks are adapted forengaging the pipeline and support at least part of the weight of thelaunched pipeline. The tensioner frame is supported via an associatedsupport assembly by the tower, and allows for displacement of thetensioner frame with respect to the tower 70 between an active position,not shown, wherein the pipeline launch trajectory 71 extends through thetensioner frame and between the tracks, so that the tracks can engage ona pipeline, and a retracted and non-operable position, as shown in FIGS.9 and 10. The pipeline installation system further comprises anabandonment and recovery system, here comprising two A&R cables andassociated A&R winches (not visible), and a sheave arrangement with foursheaves 74 supported by the pipeline launch tower 70 at an upperposition thereof.

In FIG. 10, an upper check valve 76 a and a lower check valve 76 b arevisible, for connecting a drag chain 76 c comprising electronics andhydraulics to the auxiliary trolley 50, providing a hydraulic feed e.g.for the shift cylinders 60 a and/or the pin locking cylinder 50 e.

In FIG. 10, the horizontal guide 60 of the auxiliary trolley is shown ina rotated position, which allows for a (maximum) A&R cable lengthdifference.

In FIG. 9, at the line A-A, the auxiliary trolley 50 is shown at anupper parking position. Position sensors 70 s are provided detecting theposition of the trolley. A cross-section of the auxiliary trolley 50 atthe line A-A is visible in FIG. 11A. In this position, second endconnector 77, which is positioned in the pipeline launch trajectory 71above the tensioners 73 a, 73 b, below the auxiliary trolley 50, isconnected to the auxiliary trolley 50, in particular to the collar clamp50 a provided on the trolley 50. In addition, the A&R cables areconnected to the auxiliary trolley 50, not visible in detail.

In FIG. 9, at line C-C, the auxiliary trolley 50 is shown at a secondend connector transfer position, shown in cross section in FIG. 11C.This position of the trolley is comparable with the situation in FIGS.7A and 7B, in which the load is just about to be transferred from theA&R system to the hang-off clamp 56 a, 56 b, allowing the second endconnector 77 to be disconnected from the auxiliary trolley 50, similarto the removal of pipe end 54 from the trolley in FIGS. 7A and 7B. Inparticular, a fitting piece similar to fitting piece 55 as shown inFIGS. 7A and 7B has to be removed. To this end, the tower 70 is in thisembodiment provided with a hoisting beam 80 provided with a hook 81, tocontact and hoist the fitting piece from the pipeline/pipesection/accessory such as end connector, and translate it to a parkingposition. Advantageously, the hoisting beam with hook 81 may be pivotedaway to a retracted position indicated with reference 81′. It is notedthat in FIG. 9, the second end connector 77 is indicated at a positionbelow the position of FIG. 11C, i.e. below line C-C, at the lowermostposition in which the second end connector 77 is held by the hang offclamp 76.

In FIG. 11B, the auxiliary trolley 50 is shown at an upper position inthe tower, at line B-B in FIG. 9. In FIG. 11B, the auxiliary trolley 50is depicted in a dual fall A&R position, in which the trolley parts 50′and 50″ have moved apart and the clamping parts 50 a′ and 50 a″ aremoved apart. Hence, in this situation no pipe section or accessory issupported by the clamp 50 a, but the trolley parts have moved away fromeach other allowing dual fall A&R with the cable moved apart, preventingentanglement and wire twist of the A&R cables. Part of the retractedtensioner 53 b is clearly visible.

In FIG. 9, a lowermost position of the auxiliary trolley 50, below thelowermost tensioner 73 a, is indicated by line D-D. In this position,guidance of the A&R cable by the auxiliary trolley is possible, allowingthe A&R cable to pass along the auxiliary trolley 50. In FIG. 11D, aconfiguration wherein a single A&R cable is present is shown, which isguided in the pipeline launch trajectory 71 by providing A&R cable guide50 b′ in the pipeline launch trajectory 71, accomplished by movingtrolley frame part 50 c′ along horizontal guide 60.

An alternative configuration is presented in FIG. 11E, wherein a dualA&R cable is present, comprising two A&R cables which are guided atopposite sides remote from the pipeline launch trajectory 71, byproviding A&R cable guides 50 b′ and 50 b″ at opposed sides of thepipeline launch trajectory 71, accomplished by moving trolley frameparts 50 c′ and 50 c″ along horizontal guide 60.

What is claimed is:
 1. A marine pipeline installation system for layingan offshore pipeline and/or installing a subsea riser, said system atleast being adapted to carry out the reel lay method, wherein the systemcomprises: one or more storage reels for storage of the pipeline to beinstalled; a pipeline launch tower adapted for launching the pipeline ina pipeline launch trajectory into the sea; a pipeline guide provided atan elevated position for guiding said pipeline to the pipeline launchtrajectory along said tower; one or more tensioners, each tensionercomprising a tensioner frame and multiple tracks supported by saidtensioner frame, said tracks being adapted for engaging the pipeline andsupporting at least part of the weight of the launched pipeline; thetensioner frame being supported via an associated support assembly, thesupport assembly of one or more tensioner frames being adapted to allowfor displacement of the tensioner frame with respect to the towerbetween an active position, wherein the pipeline launch trajectoryextends through the tensioner frame and between the tracks, so that thetracks can engage on a pipeline, and a retracted non-operable position;an abandonment and recovery (A&R) system comprising at least one A&Rcable and associated A&R winch and a sheave arrangement with one or moresheaves supported by the pipeline launch tower at an upper positionthereof; and an auxiliary trolley adapted to support the weight of thelaunched pipeline which is movable along a rail in the pipeline launchtrajectory when the one or more tensioner frames are in the retractednon-operable position, from a position above the uppermost tensioner toa position below the lowermost tensioner, the rail being supported bythe pipeline launch tower, wherein the auxiliary trolley comprises: anA&R connector allowing the A&R cable to be connected to the auxiliarytrolley at the position above the uppermost tensioner and therebyallowing the auxiliary trolley to lower with the launched pipelinesuspended therefrom; and a clamp comprising two clamp parts and whichare moveable between an open configuration allowing the provision of apipeline, pipe section or accessory in the pipeline launch trajectoryadjacent the clamp parts, and a closed configuration in which the clampis adapted to engage the pipeline, pipe section or accessory in thepipeline launch trajectory.
 2. The marine pipeline installation systemaccording to claim 1, the auxiliary trolley further comprising twotrolley parts, each part comprising a clamp part, the clamp parts beingmovable via respective frame parts slidably engaging with a horizontalguide of the auxiliary trolley.
 3. The marine pipeline installationsystem according to claim 2, wherein the frame parts are movable alongthe horizontal guide via shift cylinders.
 4. The marine pipelineinstallation system according to claim 1, the auxiliary trolley furthercomprising an A&R cable guide allowing the A&R cable to be guided by theauxiliary trolley and pass along the auxiliary trolley during A&R of thelaunched pipeline connected to the A&R cable, at least at the positionbelow the lowermost tensioner.
 5. The marine pipeline installationsystem according to claim 4, wherein each trolley part further comprisesan A&R cable guide.
 6. The marine pipeline installation system accordingto claim 5, the frame parts being movable along the horizontal guideallowing one A&R cable guide to be positioned in the pipeline launchtrajectory when a single fall A&R is applied, and two A&R cable guidesto be positioned at opposite sides of the pipeline launch trajectory incase of a dual fall A&R.
 7. The marine pipeline installation systemaccording to claim 1, further comprising a pipe fitting piece via whicha pipe is connectable to the auxiliary trolley.
 8. The marine pipelineinstallation system according to claim 1, wherein the clamp is a collarclamp.
 9. The marine pipeline installation system according to claim 1,wherein the clamp part is essentially C-shaped, and the clamp part isformed by a very small remaining circle-segment.
 10. The marine pipelineinstallation system according to claim 1, wherein the horizontal guideis rotatable about a point and wherein bogies with which the auxiliarytrolley is movable along the rail are mutually flexible, to compensatefor a difference in length of the A&R cables.
 11. The marine pipelineinstallation system according to claim 4, wherein the A&R cable guidecomprises A&R sheaves and/or A&R cable guidance holes.
 12. The marinepipeline installation system according to claim 1, wherein the clamp isadapted to engage a pipeline, pipe section or accessory in the pipelinelaunch trajectory at the position above the uppermost tensioner.
 13. Themarine pipeline installation system according to claim 1, furthercomprising a working platform supported by a support frame in the upperpart of the tower, whereby the support frame is adapted to allow fordisplacement of the working platform with respect to the tower, suchthat the working platform is movable into and out of the tower pipelinelaunch trajectory.
 14. The marine pipeline installation system accordingto claim 1, further comprising a J-lay installation, which J-layinstallation includes at least: a pipe loader for sequentially supplyingpipe sections to an elevated position aligned with the pipeline launchtrajectory; a pipe section alignment device for aligning a pipe sectionwith the upper end of the previously launched pipeline; and a pipesection work station, adapted for connecting the pipe section to thelaunched pipeline.
 15. The marine pipeline installation system accordingto claim 14, wherein the auxiliary trolley comprises a pipe clampadapted to engage a pipe section in the pipeline launch trajectory abovethe uppermost tensioner, and wherein the auxiliary trolley is adapted tolower the pipe section.
 16. The marine pipeline installation systemaccording to claim 15, wherein the auxiliary trolley is adapted to lowerthe pipe section and the launched pipeline connected thereto.